In traditional mechanical tolerance analysis, mechanical engineers and designers assign tolerances to dimensions and analyze the effectiveness of meeting performance requirements such as clearance around a module. It was an iterative process, with the number of steps determined by the skill of the engineer to define or modify the design. In addition, the tolerance chosen was based on perceptions the individual engineer possessed regarding the ability of machine tools to perform a particular operation, e.g., what is the best tolerance to apply to a part that will be machined on lathe?
In an effort for manufacturers to achieve higher quality, goals are set to have failure of parts down to certain limits. One such limited failure goal is called "Six Sigma" goal.
Known tolerancing software tools on the market or privately owned:
VSA (Variation Simulation Analysis )--Applied Computer Solutions; PA1 CATS (Computer Aided Tolerancing Software)--Brigham Young University PA1 GEOS--Renssalaer Polytechnic Institute PA1 Dimensional Management Software--Trikon PA1 TI/TOL--Texas Instruments and BYU PA1 Cognition
available with Autocad PA2 working on implementation with CATHA and others;
CATS has some form of Motorola Six Sigma capability. TI/TOL has some Six Sigma capability.